TUNIS, Feb 2 (Reuters) - They are at pains to assure Tunisians this is no Islamic revolution. They do not seek the presidency. They will run alongside other groups in the democracy that replaces Zine al-Abdine Ben Ali's police state.
Tunisia's main Islamist group may not have played any role in the revolution that toppled Ben Ali after 23 years, but any doubt that Ennahda would emerge as one of the largest players was dispelled with the return of its leader Rachid Ghannouchi.
Thousands thronged Tunis airport to see Ghannouchi, dwarfing any reception laid on for other exiles and alarming those Tunisians who want to keep Islam separate from the state in this French ex-colony used to decades of officially imposed secularism.
They will be watching closely in the coming months to see if Ennahda's actions match the moderation of its rhetoric.
"Tunisia will not change to adapt itself to the Islamists and their ideas. The Islamists must adapt to modern Tunisia," said Neji Bghouri, head of the journalists union.
"There is a trend in Ennahda that began to adjust to this reality but there are those who are more extreme. This is an issue of great sensitivity among Tunisia's political elite."
Despite a crackdown that saw thousands of their members jailed or exiled from the 1990s, Ennahda's supporters already appear to be more organised than any other political groups.
At Ghannouchi's homecoming, polite young Ennahda volunteers marshalled the crowds with airport security virtually invisible.
They all seemed to know each other, they had a plan and they wore white baseball caps to identify themselves as volunteers.
That is no mean feat for a group that was banned for over two decades and in a country where women who wore the Islamic head covering, or hijab, were excluded from jobs and education and men who prayed too publicly were regularly rounded up.
"Ennahda has adjusted its narrative to suit the moment and the moment is one of self-restraint," said Larbi Sadiki, a Tunisian lecturer at Exeter University.
"They will be scrutinised more than others because for a long time Tunisia and Islamist could not be spoken together."
Ennahda has been careful not to play a visible role too soon, for fear of accusations that it was transforming a popular revolt into an Islamic revolution as happened in Iran in 1979.
There, the exiled leader and cleric Ayatollah Ruhollah Khomeini became the supreme leader of a new Islamic Republic.
Ghannouchi did not return immediately. His party will field no presidential candidate. Ennahda will take part in parliament elections but Ghannouchi himself will not run for public office.
That position allays fears among some Tunisians that the Islamists will try to hijack the revolution. At the same time, if Ennahda wins a respectable number of parliament seats, it could emerge as kingmaker in presidential elections.
"Khomeini returned to a revolution of his making. Ghannouchi is coming to be part of a revolution not of his making. He can't claim this revolution," said Sadiki, who has long studied Ennahda and was on Ghannouchi's flight from London.
"They will go for 35 or 40 percent of the vote to show that they have legitimacy, nothing more. What you have to watch is what they do at the level of society, civic groups, NGOs."
No one has forgotten the 1989 election, when Ennahda was allowed to participate. It won a respectable share of the vote, alarming Ben Ali who banned Ennahda and crushed its members.
Ennahda may prove no less alarming to secular opposition groups who won less than 3 percent of the vote in the 1989 poll and will surely fear a similar trouncing by the Islamists now.
Ennahda's only rival in terms of numbers and organisation is the labour union, which briefly joined the interim government after Ben Ali's fall. It had been in alliance with Ben Ali but ultimately swung behind the revolt and is rebuilding its image.
Tunisia's handful of secular opposition parties tend to comprise a few hundred supporters coalescing around one leader.
Much has yet to be decided in Tunisia. The country needs a new election law, for instance, as existing legislation severely curbs multi-party participation. Secular groups may push for proportional representation as that model limits large groups, allows small parties a role and encourages coalition-building.
That would be to the detriment of Ennahda, though the group may well feel confident enough to accept such a concession.
"People say we face a problem in the Arab world, that our choice is either between dictators or Islamists," said Fathi Jerbi, an economics professor and opposition activist.
"We should have proportional representation so we don't end up with one large party and so no one can rule alone."
Ghannouchi has compared his party more to Turkey's moderate ruling AKP than to Egypt's harder line Muslim Brotherhood.
Indeed, Ennahda's supporters at the airport wore only light beards. Women wore headscarves but did not cover their faces.
"Ennahda would never tell you to wear the hijab. It is your choice. We are against these extremists who misrepresent us," said Samda Jbeili, who was at the airport to greet Ghannouchi.
Not all Tunisians believe this moderate stance will last. Some say a harder line could yet come to the fore. Others say Ennahda may bide its time and work at the social level to build a society amenable to political Islam.
That could take years in secular Tunisia, where the personal status code bans polygamy and protects gender equality.
"The Ghannouchi of today is not the Ghannouchi of the 1980s. It is a different Ghannouchi altogether. At the time there was talk of an Islamic state, of Islamic law," Sadiki said.
"No Islamist can really accept Tunisia's personal status code, but they have learnt what taboos to poke and what to leave and for now they will leave it. That is a huge concession."
Additional reporting by Tom Perry; editing by Giles Elgood